A curtain airbag system is configured so that in an emergency event such as in a side collision, rollover, or the like, gas for deployment is introduced from an inflator into an airbag that is stored on a roof side rail. The airbag is deployed along a side door window and the like to protect the passengers' heads. A curtain airbag system of this type is disclosed, for example, in Japanese Patent Laid-Open No. 2004-268608.
In the case where a high-output inflator (i) is used for a curtain airbag system (m) of this type, as shown in FIG. 1, gas for deployment collects in the vicinity of the inlet of a chamber (c) near a gas ejection hole of a gas guide (g) connected to the inflator (i), and therefore the internal pressure of a duct (d) increases. Then, a gas attack (e.g. overpressure condition which may lead to “bursting”) occurs in the duct (d), which makes it difficult for the gas for deployment to reach a front part (f) of the duct (d). Accordingly, the deployment of the front part of the airbag may be delayed, or the airbag may burst or rupture.
To avoid such an event, the conventional curtain airbag system (m), an inner tube (t) (or a reinforcing cloth) have been put in the duct (d) to adjust the shape and the like of an orifice (o) of the inner tube (t) provided at the inlet position of the chamber (c). By doing this, gas collection is restrained and thereby the internal pressure of duct (d) is reduced. Thereby, the gas attack is prevented from occurring to make it easy for the gas for deployment to reach the front part (f) of the duct (d) and thereby prevent the airbag from bursting.
However, if the inner tube (t) is put in the duct (d), the package size at the storage time of the curtain airbag system (m) increases, which may make the airbag system (m) incapable of being stored on the roof side rail of the vehicle. Also, if the inner tube (t) is put in the duct (d), the cost of the curtain airbag system (m) becomes high.